1. Field of the Invention
This invention relates to a transmission apparatus for sampled digital, audio data and, more particularly, to a transmission apparatus for such sampled data in which the sampled data are arranged in a two-dimensional array and error correction codes are affixed in both the row direction and the column direction of the two-dimensional array before transmission of the sampled data.
2. Description of the Prior Art
When the sampled data obtained upon digitizing analog signals, such as audio or video signals, are recorded or transmitted, these sampled data frequently undergo scrambling or error correction coding. As an example of such signal processing system, there is known a so-called block-complete type product code system in which the sampled data to be transmitted are grouped into blocks each containing a predetermined number of samples, these blocks are arrayed in a two-dimensional matrix configuration and error correction codes are annexed to each row and each column of the matrix. This block-complete type product code system is superior to the so-called convolution code system in its editing performance, and is preferred as a recording format for digital audio disks for professional use or as a format for recording video signals.
It is also known that, in the case of sampled data, obtained by digitizing analog signals, such as audio or video signals, the correlation between the adjacent sampled data is so high that, when an uncorrectable error is produced, interpolation with sampled data adjacent to the sampled data in error may be resorted to effectively. Hence, for equivalently converting a burst error into a random error, scrambling is resorted to, in which adjacent data samples, that is, an odd-numbered sample and an even-numbered sample, are transmitted such that they are spaced apart from each other.
FIG. 1 shows an example of the above mentioned block complete type product code format in which sampled data S.sub.0, S.sub.1, S.sub.2, S.sub.3, . . . of audio signals or the like are arrayed in a two-dimensional matrix configuration, the Q parity of the C2 code system is annexed to each row and the P parity of the C1 code system is annexed to each column. The Q parity for each row is arrayed in a column region at the horizontally central position in the drawing. In the left and right column regions, on both sides of the Q parity region, even-numbered sample data S.sub.0, S.sub.2, . . . and odd-numbered sample data S.sub.1, S.sub.3, . . . are arranged separately. During signal transmission, such as for recording, the sampled data are read from the extreme left column, in the vertical direction, as indicated by an arrow C, with the vertical scanning proceeding sequentially towards right in the drawing.
It will be noted that, with the above mentioned block complete type product code system, in which the sampled data to be transmitted are divided into even-numbered sampled data and odd-numbered sampled data, which are arrayed at column regions different from each other in the horizontal direction of the two-dimensional data array, the error correcting capability of a row is determined by the error correction code of the row and, if an error should occur which exceeds the error correcting capability, all of the samples of the row are determined to be uncorrectable. Since the one-row sampled data thus determined to be uncorrectable are continuous data, error concealment by the above mentioned interpolation cannot be performed satisfactorily, so that dropout may be caused in the reproduced signal. In the case of an audio signal, for example, foreign noises disagreeable to the auditory sense may be produced. In addition, if the change is acute, damage may be caused to associated apparatus or equipment.
For example, assuming that the C2 code (Q parity) shown in FIG. 1 has the capability of correcting four words, then if five or more words are in error in one row, as a result of, for example, burst errors, error correction cannot be made, such that all of the words of the row are determined to be in error. It is noted that, since the above mentioned contiguous even- and odd-numbered samples are contained in one row all words of which are determined to be in error, and these samples represent continuous data in the original signal, it is impossible to perform, for example, a mean value interpolation.